This invention relates to electromagnetic and laser treatment devices and more particularly to a cooling apparatus for use with electromagnetic and laser devices to cool the human skin during the treatment of patients.
The method of treating cutaneous lesions with light sources such as lasers is primarily based on the principal of Selective Photothermolysis proposed by Anderson (xe2x80x9cSelective Photothermolysis: Precise Microsurgery by Selective Absorption of Pulsed Radiationxe2x80x9d, Science, Volume 220, April 1983). This mechanism involves the selective absorption of light by various chromophores in the body. As these chromophores absorb the light energy, they heat up and destroy the surrounding tissue. This tissue destruction can be used as an alternative therapy to sclerotherapy in a beneficial way to remove unsightly veins and other vascular lesions since these lesions typically contain one or more highly absorbent chromophores.
The degree of selectivity and therefore tissue damage is dependent upon the type and amount of chromophore present in the tissue, the depth of the target in the tissue, and highly dependent upon the wavelength of the light being used. Since lasers are able to provide light in very precise wavelength regimes, lasers are ideal instruments for capitalizing on this principal for treatment of various lesions. This selectivity can be very beneficial in that specific lesions containing or surrounded by a particular chromophore(s) can be targeted with specific wavelengths to provide localized heating and damage while sparing surrounding tissue lacking the chromophore(s).
In practice however, the light absorption of different chromophores may be similar. For example, melanin, a chromophore which is found in the epidermis of the skin, may absorb a very similar amount of light energy at some wavelengths as the target tissue (such as the hemoglobin in a vein). Therefore, when attempting to deliver sufficiently large amounts of light energy to a target area such as a vein, the melanin in the skin above the target area may absorb enough light energy to cause epidermal damage to the skin before the target area has received sufficient energy to cause sufficient damage.
If this epidermal layer, however, is superficially cooled just prior to and/or during the application of the laser energy, the net change in temperature of the chromophores and tissue on the surface will be less and therefore the collateral damage will be less as well.
It has been known for quite some time that simple cooling techniques can be used to certain advantage in conjunction with certain therapies, including RF and laser therapies. Such simplistic cooling mechanisms include, for example, applying an ice bag to the target area for a predetermined time period prior to the application of therapeutic energy to the target area. It has also been prior described to precool the target area, as described above, and alternately provide therapeutic energy to the target area and a recooling of the target area.
It has been known for quite sometime that various cooling techniques can be used to protect the device used to provide treatment to a patient. U.S. Pat. No. 4,832,024, issued to Boussignak et al. is one such device in which a cooling fluid is flowed in a chamber between an optical fiber and the distal emitting end of a cardiovascular catheter. Various other prior art devices provide a similar cooling of the device, sometimes together with some resultant cooling of the patient target area. U.S. Pat. No. 4,733,660 issued to Itzkan is such a device in which a coolant is flowed at the distal end of a laser system, such that the laser light is passed through the liquid coolant, which is passed across the irradiated areas of the patient under treatment. U.S. Pat. No. 3,821,510 issued to Muncheryan provides a hand held laser instrumentation device in which cooling is achieved by evaporation when a coolant is sprayed from the laser device to the superficial tissue of the patient undergoing treatment. International Patent Publication WO 97-37723 similarly provides a cooling spray directly onto the tissue of the patient. U.S. Pat. Nos. 5,814,040 and 5,820,628 also spray gas and/or liquid directly onto the skin to provide cooling.
U.S. Pat. Nos. 5,057,104; 5,282,797; and 5,486,172 to Chess provide methods and apparatus for cooling the skin simultaneously with the delivery of laser light energy. Although lasers and cooling of the skin are involved and discussed, the devices described require a cooling fluid to reside over or be passed over the treatment site during laser treatment. This requires that the cooling medium be captured between two separate transparent windows which can impair visibility of the treatment area. Proper visualization of the treatment site is very important since many veins are smaller than 100 microns and difficult to target without excellent visibility of target site. A multi-layer fluid container assembly such as described is expensive, and can impair the ability of the practitioner to deliver the light to the appropriate target area.
Additionally, if not used correctly, these devices can cause relatively large refractive changes in both the incoming laser light (changing the delivered treatment spot size and therefore the treatment fluences) and in the visible light leaving the target area (making it difficult to aim the treatment beam correctly).
U.S. Pat. No. 5,344,418 to Ghaffari provides a system with a thermally conductive optical window which is cooled on one side by a cooled gas (carbon dioxide and Freon(trademark) are mentioned) and in contact with the skin on the other. This system is described to be used in combination with a feedback mechanism to control laser light delivery to the treatment site. The cooling mechanism described requires the use of complex delivery equipment and expensive (and possibly) environmentally hazardous) materials.
U.S. Pat. No. 4,140,130 to Storm provides a RF system with a cooling electrode used to direct RF energy to the target and to keep the skin cool. However, this system also calls for the cooling fluid to flow over the target area where the energy is being delivered and relates to RF devices, not to lasers.
U.S. Pat. No. 3,967,627 to Brown provides a heating and cooling applicator and control and monitoring circuitry for cooling and heating areas of the body. This device is not used for laser therapy and also has the cooling fluid passing over the entire contact area to be cooled.
It is an object of this invention to provide a simple device to cool the skin during treatment with electromagnetic energy, including treatment of vascular and cutaneous lesions, skin disorders, and the removal of hair.
It is another object of this invention to decrease the complexity of the existing art and to provide a more economical, cost-effective, and easy to use device. This is accomplished in one embodiment by using a thermodynamic property of water or other material called the xe2x80x9clatent heat of fusionxe2x80x9d to provide a temporary but relatively constant temperature at the treatment window.
It is still further an object of the present invention to provide a simpler, easier means of visualizing and cooling the target treatment zone while simultaneously delivering the electromagnetic energy.
It is yet another object of the invention to provide an apparatus which can be used for cooling the skin during treatment with electromagnetic energy in areas which are difficult to access with existing art such as the areas around the nose and ankles.